1. Field of the Invention
The present invention provides a mechanism for initiating or causing a returning movement of a tone arm of a toy phonograph which is used as a toy operated directly by the user or incorporated in a doll or in a "laughter bag" or the like.
More particularly, the present invention relates to a mechanism for causing a returning movement of a toy phonograph which is improved to afford a smooth returning of the tone arm, after a play back of the record disc, from the final to the starting positions of the reproduction, through avoiding a collision of the tone arm with the side surface of a cam for causing the upward movement of the tone arm to make the reproducing needle carried by the tone arm free from the recording groove.
2. Description of Prior Art
Some types of conventional toy phonographs incorporate a tone arm pivotally mounted and normally biased toward the starting position of the reproduction, and depressed by an intermediate sound transmitting body contacting the speaker, so as to put the reproducing needle into engagement with the recording groove formed in the surface of the record disc. The needle then slides along the recording groove, keeping a sound-transmitting contact with the sound transmitting body, so as to transmit the reproducing vibration to the speaker.
In the toy phonograph of the kind described, the automatic returning motion of the tone arm is performed by the following mechanism. As the tone arm is brought to the final position of the reproduction, a separately pivoted swingable rod is pressed by the tone arm toward the center of rotation of the record disc, so as to force the rod to ride on a cam which is provided on the upper end of the record disc driving shaft and adapted to exert an upward force on the swingable rod. As the swingable rod is lifted by the cam, the swingable rod in turn lifts the intermediate sound transmitting body to relieve the tone arm from the latter, so as to allow the reproducing needle to be disengaged from the recording groove, thereby enabling the tone arm to be freely returned by the biasing force to the starting position of the reproduction.
In such mechanism, it is necessary to position a lead groove following the final portion of the recording groove in correct alignment with the lower side of the cam contour on which the swingable rod is destined to ride, in order that the lower side of the cam may correctly confront the swingable rod when the tone arm has been brought to the final position of the reproduction, for a smooth riding of the rod on the cam contour.
Were it not for this careful setting, the swingable rod could be pressed onto the higher side of the cam on which the swingable rod cannot ride. Then, the swingable rod would have to be kept stationary, in contact with the side of the cam, until the cam is rotated to bring its lower side in alignment with the swingable rod to allow the riding of the swingable rod on the cam. During this waiting period, the reproducing needle is inevitably forced out from the lead groove, resulting in damage to the record disc, as well as to the reproducing needle.
Therefore, in a phonograph in which the record disc is demountable and interchangeable, a notch or projection is formed in the brim of the central bore of the record disc, for engagement with a mating projection or notch formed on the cam, so as to ensure the correct location of the disc relative to the cam. However, it is not easy nor convenient for an infant, who is the major user of the toy, to align the small projection and notch on the driving mechanism with each other.
Also, in a phonograph having a sole fixed record disc, the production process is inconveniently complicated due to the necessity of in-phase alignment of the cam and the lead groove.